Update As of, at least, iOS 10.2 the situation as described below has changed. The campaign_id is no longer present in the links that are used by the Apple News widget. Of course, my considerations concerning the type of traffic still apply.
If you're a bit more fanatical about you're website stats, you get some surprises every day. It could be an old page that's suddenly going viral, without any particular reason. That's a good thing, but it can sometimes lead to headaches. What's that traffic from that unknown source? Why is there a strange querystring in that URL? All too often it's 'nothing', really. A joke played on youby someone linking to your site, or a link that gets broken while it's being shared. Still, we were wondering where all that traffic with campaign_id=A100 was coming from, since mid-september.